Is re-using materials on models faster than baking textures for each model?
Even if Blender did something non-efficient, like making new shader for each object, there still would be an obvious benefit which @maddin45 mentioned. The less textures you have (the more you combine them in big atlases), the better.

As for the models themselves, think of modularity - make LEGO-like pieces and duplicate them.
http://blog.timothyeustace.com/2012/04/gears-of-war-wireframes.html